This invention relates to switching networks, and more particularly, to a type of communications network known as a nodal switching, iterative or cellular network. In such a network, each node provides the crosspoints and associated links to other nodes in the network to make it an equivalent and equi-connected member of the entire set of nodes defining the network. It has been said that one advantage of such a network is that it appears to permit growth to very large sizes, and that, during growth additions, fewer links should be required to be changed than in either single or two-sided multistage networks of conventional design. Further, since such a network is homogeneous, it should also be possible to make the assignments of lines, trunks, etc., terminating in the network independent of the traffic they offer or receive.
In my previous U.S. Pat. No. 3,916,124, I have disclosed a network permitting equi-interconnectability amongst a plurality of terminations and an arrangement which picks the most efficient path between the calling and called termination. In that patent, efficiency is determined by choosing a path of minimal length between the calling and called nodes. In my U.S. Pat. No. 3,906,175, I disclosed an arrangement offering higher traffic carrying capacity wherein a plurality of links are provided in each of the directions from each node to its nearest neighbor node. In my paper entitled, "Nodal Switching Networks," presented at the 7th International Teletraffic Congress at Farsta, Sweden, in April 1973, I disclosed that it might be advantageous to construct a nodal switching network where each node was not only connectable to its nearest neighbor nodes, but was also connectable by direct linkages to a certain number of more distant nodes. The particular plan there suggested was to employ links having lengths arranged according to what were there called binary skip distances. The advantage of using links to connect a node directly to more distant nodes is that the use of longer links decreases the number of links that have to be serially connected to each other to complete a connection between the calling and called nodes, thereby decreasing average link occupancy in the network. As a practical matter, the number of such direct links provided at each node in the network will be less than would be required to connect that node by a single direct link to every other node in the network. For example, each node may be provided with links of "unitary" length to its nearest neighbor nodes and with links to nodes twice, four times, eight times, etc., as distant. Such an array of links may, for convenience of terminology, be said to have links ordered according to binary skip distances. Truncating the number of binary skip distance links at some finite number less than that required directly to reach the most distant coordinate point in the network causes some increase of average link occupancy in the network. Using a mixed discipline of binary and fixed skip distance links, I postulated that networks could be designed where the number of links per node could be adjusted to attain the desired probabilities of blocking and link occupancy. However, my paper did not disclose any strategy for the efficient selection of links to be used in an interconnection. The present invention is directed to providing such a mechanism for implementing an efficient link selection strategy.